I don't think it would have been a problem for Sunn to scale up the 2000S to a 6 X 6550 or an 8 X 6550 and maintain the ultralinear Hafler/Laurent Dynaco circuit. As far as transformers, all that needed to be done was to commission a transformer builder to make them.
Interestingly enough, that almost had to be the case when the 1000 series amps were produced in 1968. While the 100 series Sunns were pretty much dead on the Dynaco circuit, including "Dynaco Super Fidelity" transformers, there WAS no Dynaco 4 X KT88/6550 amp, therefore no Dynaco Super Fidelity 4 X KT88/6550 transformers until 1976,
8 years after the Sunn 4 X 6550 amps were introduced.
In 1969 the SVT came out, and pretty quickly (and deservedly IMO) became the King, still is 50 years later.
Mr Sundholm sold in 1971, and I certainly can't speak for him however I'm sure if he were so inclined to make a 300, 400 watter using the Dynaco circuit he could have, and doubt that unavailability of larger ultralinear transformers would have presented a serious challenge.
As far as the <1% distortion, (as with the rated output) that's somewhere around "3" on a Sunn's volume knob. The reason that Sunns were renowned for being "loud" amps is because the were rated so low; in the actual MI world no one played them at "3". A 2000S is a solid 200+ watt amp in a live situation, one of mine that was retrofitted with a SDS Cap board benched in the 220-230 range at
around 5% THD, peaks north of 280. 5% is a usable "clean" for live use, <1% is hi-fi world clean.
Bass Gear Magazine lab tested a Reeves C225 at 256 watts, 5% THD, they did it right, that's a
solid rating. I A/B'ed a C225 next to a 2000S for literally dozens of hours during the development of the Reeves, the Reeves is more powerful - but not by much. Certainly not a 225 watt amp being A/B'ed with a 120/150 watt amp "more powerful".
As far as your theoretical question, well, you need to build one and let us know the answer.
One thing I am sure about is that no amp company is going to build a 200lb amp, there is absolutely ZERO chance of
ever selling them, and they are not about to expend any effort or $ even researching such a beast.
